A turbocharger compresses combustion air of an internal combustion engine and sends high-density air into a combustion chamber. In the turbocharger, a compressor section that compresses combustion air, and a turbine section that is driven by energy held by exhaust gas of the internal combustion engine, and that serves as a driving source of the compressor section are provided coaxially.
As such a turbocharger, an electric-motor assisted turbocharger including a motor is known. In the electric-motor assisted turbocharger, for example, in a case where an internal combustion engine is in a low load state, and an amount of exhaust gas is not sufficient, the motor is energized, and driving of a compressor section is assisted by driving force of the motor.
PTL 1 discloses a motor of an electric-motor assisted turbocharger including a motor rotor provided in a shaft extension section that extends a rotor shaft of a turbine toward an intake air introduction passage side, and a stator provided around the motor rotor. The motor rotor is mounted on the shaft extension section of the rotor shaft of the turbine, so that this motor is supported by a bearing (bearing of the rotor shaft) supporting a turbocharger body. In such a motor, the motor rotor itself does not have a bearing, and a so-called motor overhang structure is employed.
The stator of the motor in the motor overhang structure is located in a cylindrical housing supported by a turbocharger body. When the turbocharger is assembled, the motor rotor is mounted on the rotor shaft, the housing is thereafter fixed to the turbocharger body, and then the stator is inserted (pressed) into the inside of the housing to be fixed to the housing by predetermined fitting.